Rational design of an improved induction scheme for recombinantEscherichia coli

In Escherichia coli, strong overexpression of a recombinant protein has been shown to be deleterious due to a heavy metabolic burden on the host cell, which may completely cease cell growth before maximum product accumulation has occurred. Aiming at a reduction of very high product formation rates, we engineered E. coli strains by mutating the Leloir pathway for galactose metabolization, so that galactose can be utilized to induce lac derived promoters. The induction with galactose was effective in every strain and expression construct tested, and it reduced the metabolic burden on a highly overproducing clone so that cell growth and product accumulation could be maintained for several generations.